Revivification and preservation of chemical solutions



1933. s. TIJMSTRA REVIVIFICATION AND PRESERVATION OF CHEMICAL SOLUTIONSFiled Aug. 30, 1929 i 25 absolute without having any gage pressure.

Patented Aug. 15, 1933 UNI ED STATES PATENT OFFICE REVIVIFIOATION ANDPRESERVATION F v CHEMICAL SOLUTIONS Sijbren Tiimstra; Clayton,Monassignorto Shell Petroleum Corporation, a vCorporation of VirginiaApplication August so, 1929.- Serial Nb. 389,382

6 Claims. 01. 23-44) This invention relates: to the revivification andpreservation of chemical solutions.

Heretofore in practice, it hasbeen usual to keep a sodium bicarbonatesolution, commonly used as a fire extinguishing liquid, in open tanks.

The solution breaks down under these conditions aftera period of timeinto sodium carbonate and carbon-dioxide which deteriorates the solutionfor use as a fire extinguishing liq- 10 uid. In order to revivify thesodium carbonate solution, it is necessary toset up a special set ofconditions so that a partial pressure of carhon-dioxide, in the vaporphase is maintained above thedeteriorated solution. The partial pressureof'the carbon-dioxide is to be maintained at somewhat more than 0.4atmosphere 1 at 100 1 To accomplish this condition satis factorily,qitis necessary that the deteriorated solution should be revivified in atank from zowhioh air has been excluded when the atmosphere of thecarbon-dioxide. and. water vapor are present above the deterioratedsolution without any air. The partial pressure of carbondioxide in suchcase can be about 1.0 atmosphere Were itattempted to merely inject thecarbon-dioxide gas into a gas-type tank, it would be impossible toobtain the required pressure for the absorption of thecarbon-dioxideWithout, at the same time, raising the pressure in. the,tank to such a degreeas to damage the tank by over pressure. "Ithasbeen, discovered that by the method hereinafter described a satisfactorymeans of revivifying the deteriorated sodium-carbonate SOIUtJlOl'lutOform a sodium bicarbonate solution ay be accomplished without danger ofdamaging the tank eitherby an excess pressure to expand the walls of thetank orpby. a sufiiciently reduced pressure to collapse the walls of thei 40 tank; and that when the solution has been revivified, itmay bepreservedby maintaining an atmosphere of the carbon-dioxide in contactwith the surface of the liquid in the tank'and that even though there isa variation in pressure,rdue to atmospheric .conditionathe tank willbeprotected against outward expansion or collapse by, the control meanshereinafter more particularly described.

, i i It should be understood that; while the invenp tion isparticularly applicable for the lpurpose of revivifyingz a sodiumcarbonate solution to form a sodium bicarbonatesolution, uitis also"applicable in, all cases where itis desired to revivify a deterioratedsolution by the absorptionor algas.

The general object of the invention'is, therefore, to provide animproved method for revivifying and preserving chemical solutions thatdeteriorate in the receptacles or vessels in which the solutions arekept.

Other objects will appear from the following description, referencebeingmade to the accompanying drawing wherein I have illustrated anappropriate apparatus for the practice of the present invention and inwhich 7 Fig. li's across sectional view of a tank con- 7 taining thesolution and equipped with means for the practice of the invention.

Fig. 2 is a side elevation of the tank with the parts shown in section.

The tank shown in the drawing is a gas tight tank including a sidewall 1and a top wall 2, forming the impervious walls of an enclosure I forconfining the solution. A vertical transverse wall 3 extends across oneof the lateral portions by a. space 4 through which the solution maypass into and out of the spacefi between the walls 1' and 3. A top wall6forms an impervious connection with the walls 1 and 3 and constitutesthe top wall of the enclosed space 5. A by-pass pipe 7 has one endopening through the wall 1 above the wall 6 and .has its other endopening into the space'5 closely below the wall 6 and is controlled by avalve 8 whereby the passage of the gas through said pipe 7 may becontrolled.

I A pipe9 extends through the walll and opens 9 into branch pipes 10extending in opposite dipipes 11 have through their upper sides numerousoutlet openings 13. l

Another pipe 14 extends through the wall 1 of the tank and into thespace 5 and opens'into a pair of oppositely extended pipes 15, havingthrough their upper sides numerous outlet open: ings 16'.

The top wall 2 of the tank is conical and at its apex has an outlet pipe17 which may be 1107 opening through the tank wall 1 below thenoropenedand closed by manipulation of a valve 18.

A vertical pipe 19 opens into the tank through the lower portion of thetop wall 2 and extends downwardly at the outer side of the wall 1 andopens into a surge tank 20 which is designed and adapted to contain -aquantity of water. The tank 20 opens into a laterally extended pipe 21communicating with the .vertical pipe 22, which opens at its upper endinto a surge tank 23 that is open at the top. The tank 20 is equipped atits side with a glass 'gage tube 24, of familiar construction, whichwill visually indicate the amount and condition of water in the tank 20.The pipes 21 and 22 open into the lower and upper ends, respectively,

of the tube 25' of a glass gage, of familiar con struction, which willvisually indicate the heighth to which the water extends in the pipe 22.The pipe 19 has a lateral outlet pipe 26 equipped with a valve 2'?whereby any portions of the contents of the pipe 19 above the pipe 26may be withdrawn forinspection or other purposes. v Y t The tube 28 of aglass gage has its lower end mallevel of the liquid or solution in saidtank, and its upper end opening into the top wall 2 above the normallevel of the liquid or solution in said tank. The normal level of theliquid or solution within the tank is approximately at the line 29. Thepipe 19 is equipped with a valve 30 above the opening to the pipe 26.The valve 3Qmay be operated to open or to close the pipe 19, as desired.1

In practicing the invention by the apparatus described, the solution maybe introduced into the tank through the pipe. 17 or other suitableconnection so thatit completely fills the space 5' and the greaterportion of the main tank, thesurface of the solution being, forillustration, approximately at the line 29.

The valves 8, 27 and 30are closed and the valve 18. is opened. Next agas is forced through the pipe 1e and into thebranch pipes 15 and intothe space 5 through the openings 16 in said pipes 15. The gas will riseto the top of the space 5 and eject from the space Sthe solutioncontained therein, the solution being forced :-from said space 5 throughthe opening 4 to the ..pletely to fill the tank. Thereupon thevalve.

18 is closed, and the introduction of the gas through the pipe 1%isreduced sufficiently that only a slight pressure will be maintained inthe tank. .It is now clear that all air has been *forced from the spacein the top of thetank and that the tank contains only the solution andthe gas under a slight degree of pressure.

Next, the by-pass valve 8 is opened and the .gas is caused to howthrough the pipe linto the upper portion of the. tank. This causes thechemical solution to flow from the main tank through the opening 4 'intothe space 5, so that as the levelof. the. solution in the main tank:becomeslowered, the space in the main tank above the level of thesolution is filled with the gas.

When the upper part of the tank has thus been filled with an atmosphereof gas, the absorption of the gas by the liquid progresses throughoutthe contacting surface of the liquid with the gas. Thus, the pressure inthe tank tends to reduce. The supply of gas through the pipe i l is nowdiscontinued and the major supply is provided through the pipe 9 and thebranch pipes 16 and 11', the gas being injected through the body of theliquid.

As the process of revivifying the solution usually requires aconsiderable length of time, means ar providedfor preventing damage tothe tank either by an excess pressure or by a reduced pressure. It isimpractical to control the rate offlow of the gas so that it may becoordinated exactly with the rate of absorption, therefore an over orunder pressure in the tank may result during the course of therevivifying operation. To protect the tank, therefore, against damage,means are provided for controlling the pressure in the tank by relievingexcess pressure generated by the gas or by supplying a lack of pressureby reason of illSllfficient supply of gas.

In orderto accomplish this result, the valve 30 in the pipe 19 isopened, and the surge tank 20 and its connections are brought intooperation. I

The surge tank 20 and its connection constitutera safety device toprevent over or under pressure in the tank 1. In practice, a sufficientquantity of water or other fluid under normal conditions accumulates inthe bottom of the tank 20, to approximately the depth indicated inFig. 2of the drawing. That is to say, a suilicient level of liquid ismaintained in the tank to constitute a seal when pressure does notexceed or fall below the predetermined pressure for the tank 1. If thepressure in the tank 1 exceeds a desired degree, the liquid is forcedfrom the tank 29 into the line 22 and into the open tank 23 and theexcess pressure will be relieved by the fluid pressure bubbling throughthe liquid in the tank 23.- When the pressure again returns to normal,the liquid will flow bygravity into the bottom of the tank 20. If thepressure in the tank 1 reducesv below the predetermined minimum, airwill be, drawn through the liquid seal in the bottom of the tank 20 bysuction and will thereupon enter the tank and relieve the reducedpressure. It is, of course, not desirable to permit the accumulation ofany substantial amount of air inthe tank '1 above theliquid and, if anundue amount does accumulate, it may be driven out or" the tank bytheioperation above described for relieving thetank of. air.

The surge tank 20 andv its connections thus avoid the danger of thepressure in the tank 1 becoming lessthan atmospheric and remaining at,less than atmospheric pressure. For, it' is clear that should thepressure in the tank 1 become'less than approximately0.95 atm. absolute,the water will be Withdrawn from the opentop tank 23 and the pipe 22 anddischarged into tank 20, and a suflicient amount of atmosphere willbeadmitted to the main tank through tank 23 to reduce the pressuredifierential between the main tank land the atmosphere. The surge tanksalso prevent the formation in the-main tank of a pressuremore thanapproximatelydl atm. above atmospherimfor when the pressure in' the maintank becomes more than that stated;

, through the pipe 22 into the surge tank 23 and the excess gas will-:bedischarged through the water in tank 23 into the atmosphere, thusreducing the pressure in the main tank. The gages 24 and 25 indicatethese conditions.

It should be understood that, after the solution has once beencompletely revivifi'ed; the" supply of gas is then discontinued exceptfor intermittent admission of gas to supply any leakage and the liquidsremain stored in the be readily understood from the 'foregoingdescription.

Iclaiml i i 1 The method of causing absorption of a gas by a liquidwhich includes confining the liquid in a tank, venting the tank at thetop, introducing and confining the gas below the level of the liquid ina sealed chamber in communication with the liquid in the tank near thebottom of the chamber to .cause the level of the liquid to rise to, thetop of the tank thus ejecting from the top of the tank the air which wasoriginally contained therein above the original level of the liquid andsealing the vent.

2; The method of causing absorption of a gas bya liquid which includesconfining the liquid in a tank, venting the tank at the top,

introducing and confining the gas below thelevel of the liquid in asealed chamber in communication with the liquid in the tank near thebottom'of the chamber to cause the level of the liquid to rise to thetop of theltank thus ejectlevel of the 1iqui d, sealing the vent,releasing ing from the top of the tank the air which was originallycontained therein above the liquid the confined gas from the chamber andpermitting it to flow to thetop of the liquid.

3. The method of causing absorption of a gas'by a liquid which includeconfining the liquid in a tank, venting the tank at the top,

introducing and confining. the gasbelow the level of the liquid in asealed chamber in communication with the liquid in the tank near thebottom of the chamber to cause the level of the liquid to rise to thetop of the tank thus ejecting from the top of the tank the air which wasoriginally contained therein above the origtank at] the top, introducingand confining the cation with the solution in the tank near the bottomof the chamber to cause the level of the solution to rise to the top ofthe tank, thus ejecting from the top of the tank the air which wasoriginally contained therein above the level of the solution, andsealing the vent.

5.,The method of treating sodium carbonate solution with carbon dioxidewhich includes confining the solution in a tank, venting the tank atthe:top, introducing and confining the carbon dioxide in vapor phasebelow, the level of the liquid in a sealed chamber in communication withthe liquid in the tank near the bottom of the chamber to cause the levelof the liquid to rise to the top of the tank, thus ejecting from the topof the tank the air originally confined therein above the level of thesolution, sealing the vent, releasing the confined carbon dioxide fromthe chamber, and permitting it to flow to the top of the solution.

'6. The method of treating sodium carbonate solution with carbon dioxidewhich includes confining the solution in a tank, venting the tank at thetop, introducing and confining carbon dioxide in vapor phase below thelevel of the liquid in a sealed chamber in communication f

